The present invention relates to an operating method for a rolling train for rolling a flat workpiece in at least one rolling stand of the rolling train.
The present invention further relates to a computer program comprising machine code which can be directly executed by a control computer for a rolling train for rolling a flat workpiece.
The present invention further relates to a control computer for a rolling train for rolling a flat workpiece.
The present invention further relates to a rolling train for rolling a flat workpiece, said rolling train being equipped with such a control computer.
Such subject matter is disclosed in WO 2006/063 948 A1, for example.
According to the known operating method, the set variables are used in conjunction with the initial data, which describes the flat workpiece before rolling in the rolling stand, and the stand data of the rolling stand, to describe the resultant roll nip during the rolling of the flat workpiece in the rolling stand. As part of the rolling schedule calculation on the basis of the initial data, the stand data and the set variables, the control computer determines, by a model, expected variables which are expected for the flat workpiece when the flat workpiece is rolled in the rolling stand using the set variables. As part of the rolling schedule calculation, the control computer varies at least one of the set variables according to a strategy, such that the determined expected variables are brought at least close to the final variables. The control computer transfers the varied variables that are determined by the rolling schedule to a basic automation system of the rolling stand, such that the flat workpiece is rolled in the rolling stand in accordance with the varied variables.
DE 10 2009 043 400 A1 discloses a system for model-based determination of desired actuator values for a hot broad strip train comprising a plurality of rolling stands. According to this system, a desired target contour of the roll nips of the stands can be adjusted by implementing the desired actuator values. In a first part of the method of this system, a desired speed taper of the hot strip after each stand is prescribed. In the second part of the method, strip flatness models are used to determine values for strip thickness contours on the delivery side of the stands. In the third part of the method, rolling force distributions that must be applied for each stand are specified by material flow models. In the fourth part of the method, the target contour is determined for the strip travel actuators. In the fifth part of the method, the desired actuator values for each stand are calculated from the target contour by an optimization method.
The method described in DE 10 2009 043 400 A1 is applied while the flat workpiece is passing through a multi-stand rolling train. Measurement variables on both feed and delivery sides of all participating rolling stands are required in order to perform the method.
Equivalent contents are disclosed in DE 10 2009 043 401 A1.
When rolling metal, the shape of the workpiece is an important variable from the beginning of the process onwards and via all of the intermediate process. In addition to thickness, width, profile and flatness, the taper (i.e. the asymmetric portion of the thickness over the width of the flat workpiece) and the camber (i.e. the curvature of the flat workpiece in the rolling plane) are also important characteristic variables. Both taper and camber are undesirable, since these variables (when not equal to 0) complicate and even in some circumstances prevent the subsequent process or result in spoilage.
The taper and the camber are also closely linked as a result of the material retention. For example, if a slab which is cold on one side enters the rolling stand, the colder side is rolled less effectively than the hotter side due to the greater rolling force on one side and the associated greater frame stretch of the rolling stand on one side (in the absence of any other control intervention). This causes a thickness taper and a corresponding camber to develop. However, if an already tapered flat workpiece enters the rolling stand and the thickness taper is eliminated during the rolling of the flat workpiece, a camber is generated by the rolling.
If the flat workpiece already has a thickness taper, the related art often provides for the upper set of rollers and the lower set of rollers to be swiveled relative to each other, such that the relative taper is retained during the rolling pass and consequently no curvature (=camber) is generated. The swiveling is effected manually by an operator on the basis of the observation of the workpiece. Methods which automatically support the operator by anticipating or at least limiting these manual interventions are also known. These methods are based on measurements of differential rolling forces and adjustments, and are therefore implemented in the context of the basic automation system.
In the case of tapered slabs, i.e. slabs having a thickness taper, methods are also known which eliminate the taper while nonetheless preventing the development of a camber by imposing asymmetrical tension distributions. This is achieved by producing a cross flow in the material.
It is difficult or even impossible, solely on the basis of the rolling force signal, to determine a desired value for a correction element by which the delivery taper can be corrected.